Boris Johnson said the government should ‘wack through’ gay marriage legislation (Picture: PA)

Boris Johnson and Michael Gove have defied Conservative Party traditionalists by launching a campaign group backing gay marriage.

London’s mayor and the education secretary joined senior Tory figures calling for same-sex weddings to be allowed in places of worship.

In a letter to the Sunday Telegraph announcing the formation of the group, they declared: ‘Marriage should be open to all, regardless of sexuality.’

Mr Johnson later said the government should ‘get on and whack through’ the legislation.

‘It is perfectly obvious that the constituency is there for doing this,’ he told Sky News’s Murnaghan programme.

The campaign group has been put together by former police minister Nick Herbert and includes transport secretary Patrick McLoughlin, who is Catholic, foreign office minister Alistair Burt, an evangelical Christian, and former ministers Lord Fowler and Nicholas Soames.

More than 100 Tory MPs have indicated they will oppose a change in the law, despite David Cameron’s backing for the move.

But former prime minister Sir John Major backed Mr Cameron, calling his stance ‘courageous and genuine’.